1. Field of the Invention
The present invention relates to a centrifugal pump that applies pressure by driving an impeller by magnetic coupling, and in particular, to a centrifugal pump suitable for liquid such as chemical solutions containing fine particles, and liquid such as chemical solutions that tend to seize.
2. Description of Related Art
Conventionally, general pumps have a shaft seal mechanism (shaft seal unit) to prevent fluid in a pump chamber from leaking outside from a shaft and to prevent sucking in of air or the like from outside. Practical shaft seal mechanisms include gland packing, labyrinth or mechanical seals, etc., which are selected depending on the pump operating environment, cost, etc.
Some of the pumps described above are centrifugal pumps, which are configured to supply pressure energy or speed energy in a radial direction to fluid using a centrifugal force by rotating an impeller in a casing.
Some of the centrifugal pumps described above rotationally drive a pump rotor which is stabilized by permanent magnets acting in the radial direction on a ferromagnetic area of the pump rotor (for example, refer to JP2869886B2).
A known centrifugal pump is provided with permanent magnets at the shaft of an impeller and rotates the impeller by a driving unit that is provided at the casing side and that generates a rotating magnetic field. In this case, it is disclosed that the impeller is supported by a pivot bearing, and for the materials of the pivot shaft and a pivot bearing, materials with different hardnesses, such as a combination of ceramic and ultra-high-molecular-weight polyethylene, is selected (for example, refer to JP2002-349482A).
Meanwhile, centrifugal pumps equipped with a shaft seal mechanism have problems with the occurrence of leakage from a shaft seal component, the occurrence of wear and friction, and limited heat-resistant temperature and pressure resistance. This requires the development of a centrifugal pump that needs no shaft seal mechanism and also has no leakage.
The present invention is made in consideration of the above-described circumstances, and it is an object thereof to provide a centrifugal pump that needs no shaft seal mechanism and has no leakage. In particular, an object of the present invention is to provide a centrifugal pump with a configuration that is suitable for liquid such as chemical solutions containing fine particles, and liquid such as chemical solutions that tend to seize, and moreover, that can easily be reduced in size.